The present invention relates to a predictive coding system which performs highly efficient coding of image signals as of a commercial TV or conference TV system through utilization of high correlation between adjacent picture elements in a picture, and more particularly to a predictive TV signal coding system which permits easy materialization of various predictive coding systems.
Standard TV signals at present consist of pictures called frames which are sent at the rate of 30 per second for NTSC system and 25 per second for
and SECAM systems, and each frame is subjected to interlaced scanning every other scanning line and, therefore, consists of two successive fields. Elements making up the pictures are commonly referred to as "picture elements", but since digital processing is considered in the present invention, each sample obtained by sampling will hereinafter be called a picture element. Accordingly, in this instance the position of each picture element in the picture depends upon the sampling frequency for digitizing a signal.
In general, digital processing which retains the real time property calls for a high-speed operation. That is, the real time property cannot be maintained unless the coding of one picture element is processed within its one sampling period. However, it is very difficult to provide an effective predictive coding system for TV signal of simplified hardware without lowing the coding efficiency and increasing the amount of hardware used.